Experiments were conducted to obtain row-by-row heat and mass transfer data during condensation of downward-flowing three-component zeotropic mixture R407C in a 3×15 staggered bundle of horizontal low-finned tubes. The refrigerant mass velocity ranged from 4 to 23 kg/m2s and the condensation temperature difference from 2.8 to 12 K. The results were compared with those for R134a. The heat transfer coefficient for R407C was considerably lower than that for R134a, with the difference being more significant for lower mass velocity and lower condensation temperature difference. The effect of vertical row number on the heat transfer coefficient was not so significant. The distribution of vapor temperature in the tube bundle was almost uniquely dependent on the quality. The mass transfer in the vapor phase was discussed in terms of the superficial heat transfer coefficient. On the basis of the analogy between momentum and mass transfer, a correlation for the superficial heat transfer coefficient was obtained.